This invention related to a composition that is useful for making circuit boards.
Circuit boards are widely used in the electrical industry for radio, television, appliances, industrial and electrical equipment. In general, circuit boards are made by impregnating a woven fiberglass sheet with a resin and laminating copper sheet to one or both sides of the resin impregnated fiberglass sheet; then an electrical circuit is etched into the copper to form the circuit board. Electrical connections are usually soldered to the board when the board is utilized.
Polyimide resins have been used to impregnate these fiberglass sheets and form excellent quality circuit boards which have resistance to high temperatures, low thermal expansion and good electrical properties, such as a high level of resistivity. However, these boards are of a relatively high cost in comparison to circuit boards made from an epoxy resin impregnated fiberglass sheets. Circuit boards of epoxy resin impregnated fiberglass sheets are not resistant to high temperatures and have poorer electrical properties and a higher level of thermal expansion in comparison to circuit boards of polyimide resin impregnated fiberglass sheets.
There is a need for a composition that has a cost that is comparable to epoxy resins but that will form a circuit board having physical and electrical properties close to polyimide circuit boards but substantially better than epoxy resin circuit boards. The novel composition of this invention will form circuit boards that have such properties.